/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.http.converter.xml;

import java.io.IOException;

import javax.xml.transform.Result;
import javax.xml.transform.Source;

import org.springframework.beans.TypeMismatchException;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.lang.Nullable;
import org.springframework.oxm.Marshaller;
import org.springframework.oxm.MarshallingFailureException;
import org.springframework.oxm.Unmarshaller;
import org.springframework.oxm.UnmarshallingFailureException;
import org.springframework.util.Assert;

/**
 * Implementation of {@link org.springframework.http.converter.HttpMessageConverter HttpMessageConverter}
 * that can read and write XML using Spring's {@link Marshaller} and {@link Unmarshaller} abstractions.
 *
 * <p>This converter requires a {@code Marshaller} and {@code Unmarshaller} before it can be used.
 * These can be injected by the {@linkplain #MarshallingHttpMessageConverter(Marshaller) constructor}
 * or {@linkplain #setMarshaller(Marshaller) bean properties}.
 *
 * <p>By default, this converter supports {@code text/xml} and {@code application/xml}. This can be
 * overridden by setting the {@link #setSupportedMediaTypes(java.util.List) supportedMediaTypes} property.
 *
 * @author Arjen Poutsma
 * @since 3.0
 */
public class MarshallingHttpMessageConverter extends AbstractXmlHttpMessageConverter<Object> {

    @Nullable
    private Marshaller marshaller;

    @Nullable
    private Unmarshaller unmarshaller;


    /**
     * Construct a new {@code MarshallingHttpMessageConverter} with no {@link Marshaller} or
     * {@link Unmarshaller} set. The Marshaller and Unmarshaller must be set after construction
     * by invoking {@link #setMarshaller(Marshaller)} and {@link #setUnmarshaller(Unmarshaller)}.
     */
    public MarshallingHttpMessageConverter() {
    }

    /**
     * Construct a new {@code MarshallingMessageConverter} with the given {@link Marshaller} set.
     * <p>If the given {@link Marshaller} also implements the {@link Unmarshaller} interface,
     * it is used for both marshalling and unmarshalling. Otherwise, an exception is thrown.
     * <p>Note that all {@code Marshaller} implementations in Spring also implement the
     * {@code Unmarshaller} interface, so that you can safely use this constructor.
     *
     * @param marshaller object used as marshaller and unmarshaller
     */
    public MarshallingHttpMessageConverter(Marshaller marshaller) {
        Assert.notNull(marshaller, "Marshaller must not be null");
        this.marshaller = marshaller;
        if (marshaller instanceof Unmarshaller) {
            this.unmarshaller = (Unmarshaller) marshaller;
        }
    }

    /**
     * Construct a new {@code MarshallingMessageConverter} with the given
     * {@code Marshaller} and {@code Unmarshaller}.
     *
     * @param marshaller the Marshaller to use
     * @param unmarshaller the Unmarshaller to use
     */
    public MarshallingHttpMessageConverter(Marshaller marshaller, Unmarshaller unmarshaller) {
        Assert.notNull(marshaller, "Marshaller must not be null");
        Assert.notNull(unmarshaller, "Unmarshaller must not be null");
        this.marshaller = marshaller;
        this.unmarshaller = unmarshaller;
    }


    /**
     * Set the {@link Marshaller} to be used by this message converter.
     */
    public void setMarshaller(Marshaller marshaller) {
        this.marshaller = marshaller;
    }

    /**
     * Set the {@link Unmarshaller} to be used by this message converter.
     */
    public void setUnmarshaller(Unmarshaller unmarshaller) {
        this.unmarshaller = unmarshaller;
    }


    @Override
    public boolean canRead(Class<?> clazz, @Nullable MediaType mediaType) {
        return (canRead(mediaType) && this.unmarshaller != null && this.unmarshaller.supports(clazz));
    }

    @Override
    public boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType) {
        return (canWrite(mediaType) && this.marshaller != null && this.marshaller.supports(clazz));
    }

    @Override
    protected boolean supports(Class<?> clazz) {
        // should not be called, since we override canRead()/canWrite()
        throw new UnsupportedOperationException();
    }

    @Override
    protected Object readFromSource(Class<?> clazz, HttpHeaders headers, Source source) throws IOException {
        Assert.notNull(this.unmarshaller, "Property 'unmarshaller' is required");
        try {
            Object result = this.unmarshaller.unmarshal(source);
            if (!clazz.isInstance(result)) {
                throw new TypeMismatchException(result, clazz);
            }
            return result;
        } catch (UnmarshallingFailureException ex) {
            throw new HttpMessageNotReadableException("Could not read [" + clazz + "]", ex);
        }
    }

    @Override
    protected void writeToResult(Object o, HttpHeaders headers, Result result) throws IOException {
        Assert.notNull(this.marshaller, "Property 'marshaller' is required");
        try {
            this.marshaller.marshal(o, result);
        } catch (MarshallingFailureException ex) {
            throw new HttpMessageNotWritableException("Could not write [" + o + "]", ex);
        }
    }
}
